Note on Introduction to Algae

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Algae are kept in division Thallophyta along with fungi. They differ from fungi in the presence of chlorophyll pigment and mode of their nutrition.

General characteristics of algae

Algae are of universal occurrence. They are found in the variety of habitats like some member of algae grow in fresh water. Some are grown in marine water, on moist soil, on moist rocks, on snow, within or in animal or plant bodies.

Epizoic- algae grow on the outer surface of the animal body.

Endozoic- algae grow in the inner part of the animal body.

Epiphytic- algae grow in the plant body.

Endophytic- algae grow inside the plant body.

Gametophytic plant body of algae is thallus which may be branched or unbranched

Some members of algae are unicellular. Eg; Chlamydomonas. Some are multicellular. eg; macrocystis

Each of the cells is bounded by the cellulosic cell wall. It is further differentiated into the outer mucilaginous sheath and inner cellulosic layer. Mucilaginoussheath makes plants body slippery to touch and protect from dead and decaying of the plant body.

Process involved in sexual reproduction

Sexual reproduction takes place by isogamy, anisogamy, and oogamy.

Isogamy

The fusion process of morphologically similar but physiologically dissimilar gametes is called isogamy. Male having the positive strain and female having negative strain are involved. Due to the opposite strains, they come close to each other and fuse together to form a diploid zygote. This process is also called conjugation.

Anisogamy

The fusion process of morphologically as well as physiologically different gametes is called anisogamy. The male is smaller and motile and female is larger and non-motile. Such types of gametes are called anisogamete and fusion process is called anisogamy or anisogamous sexual reproduction.

Oogamy

The fusion process of male gamete antherozoid and female gamete ovum or egg is called oogamy. Male gametes are developed in antheridium and female gametes are developed in archegonium. If the antherozoid and egg are developed in a separative reproductive sex organ fertilized product is zygote called oogamous type of sexual reproduction.

Classification of algae

On the basis of dominant photosynthetic pigment, storage food material, and cell wall component division algae are divided into three classes;

Chlorophyceae(Green algae)

Phaeophyceae(Brown algae)

Rhodophyceae(Red algae)

S.N

Characters

Green algae

Brown algae

Red algae

1

Habitat

They are commonly found in fresh water. Some are terrestrial.

They are commonly found in cold marine water. Very few are freshwater.

They are commonly found in hot marine water.Eg; Batrachospermum is a freshwater red algae.

2

Habit

Unicellular and multicellular form are present.

Only multicellular form is present.

Unicellular and multicellular form are present.

3

Cellwall component

Cellulose, hemicellulose, and pectin.

Cellulose, pectin, algenic acid, ficoidin, and fucin.

Cellulose, pectin, agar and carrageenan.

4

Dominant photosynthesis pigment

Chlorophyll-a

Chlorophyll-b

carotene and xanthophyll

Chlorophyll-a

Chlorophyll-c

Fucoxanthin and fucocynin

Chlorophyll-a

Chlorophyll-d

r-phycoerythrin and allophycoerythrin

5

Storage food

Starch

Mannitol or laminarin

Floridian starch

6

Motile phase

Motile phase is present.

Motile phase is present.

Motile phase is absent.

7

Reproduction

It reproduce by vegetative, asexual and sexual methods.

Sexually reproduce by isogamy, anisogamy, and oogamy.

It reproduces by vegetative, asexual and sexual methods.

Sexually reproduce by anisogamy and oogamy.

It reproduces by vegetative, asexual and sexual methods.

Sexually reproduce by oogamy.

8

Example

Spirogyra, volvox, Chlamydomonas.

Fucus, laminaria, actocarpus, sargassum.

Batrachospermum, Gelidium, polysiphonia.

9

It is represented about 7000 species.

It is represented about 2000 species.

It is represented about 5000 species.

Molecular formula of;

Chlorophyll-a - C55H70O5N4 mg

Chlorophyll-b- C55H70O6N4 mg

Carotene- C40H56

Xanthophyll- C40H56O2

Economic importance of Algae

Seaweeds such as Laminaria japonica and religiosa are used for the treatment of goiter as they contain iodine.

Gelidium (as agar) is used in medicine as a laxative and in a culture medium for the growth of bacteria and for the manufacture of pills and ointments.

Extracts of some algae like Digenea, Codium, alsidium, and Durvillea are effective vermifuge.

Corallina cure worm infections and its extracts are used for the treatment of kidney, bladder and lungs diseases.

Chlorella culturing tanks are kept during space journey because of their rapid oxygen liberating capacity so that cosmonauts could breathe clean air.

Algae are of universal occurrence. They are found in the variety of habitats like some member of algae grow in fresh water. Some are grown in marine water, on moist soil, on moist rocks, on snow, within or in animal or plant bodies.

Algae are kept in division Thallophyta along with fungi.

Embryo stage is absent in algae.

The fusion process of morphologically similar but physiologically dissimilar gametes is called isogamy.

The fusion process of morphologically as well as physiologically different gametes is called anisogamy.

The fusion process of male gamete antherozoid and female gamete ovum or egg is called oogamy.